Hydraulic centering device



July 20, 1965 D. E. RUNKLE HYDRAULIC CENTERING DEVICE Filed May 29, 1963 INVENTOR United States Patent 3,195,570 HYDRAUUC QENTERHNG DEVECE Dean E. Rennie, South fiend, 1nd., assigner to The Bendix torporation, South Bend, 1nd., a corporation of Delaware Filed May 29, 1963, Ser. No. 284,291 3 Claims. (Cl. 137-596) This invention relates to hydraulic power steering and more particularly to means for hydraulically centering a power steering control valve.

Experience has shown that due to normal manufacturing tolerances, it is almost impossible to accurately locate a valve spool in its housing so that there will be no differential in pressure between the two cylinder ports when the spool is mechanically located in its center or straight ahead driving position.

Accordingly, it is an object of this invention to provide a device which will, for the straight ahead driving position, balance the pressures at the cylinder ports regardless of variations in manufacturing tolerances.

Another object of this invention is to provide a device which, if desired, can, for the straight ahead driving position, be adjusted so as to create a predetermined difierential in cylinder port pressures so as to balance the forces exerted by a power cylinder having differential piston areas.

A further object of this invention is to provide a device which will adjust the pressures at the cylinder ports without varying the inlet pressure.

More particularly, it is an object of this invention to provide, in connection with an open center spool type valve, inlet orifice areas interposed between the inlet pressure port and the land orifice areas formed by the associated lands of the spool and housing, which inlet orifice areas are varied by a centering plunger in order to offset the manufacturing tolerances affecting the land orifice areas.

The above and other objects and features of the invention will become apparent from the following description of the device taken in connection with the accompanying drawing which forms a part of this specification and in which:

FIGURE l is a sectional view of an open center power steering valve incorporating my invention; and

FIGURE 2 is an enlarged fragmentary sectional view of the valve shown in FIGURE 1.

Referring to FIGURE l of the drawings, numeral designates a control valve comprising a housing member a 12 having a bore 14 therein. A valve member 16 lies within the bore 14 and is movable in opposite directions from a normally neutral or center position, thereby controlling flow in the hydraulic system. The valve member 16 is formed with two annular channels 18 and 20 which communicate with cylinder ports 22 and 24 respectively. The bore 14 of the housing is provided with annular channels 26, 28 and 30. Annular channel 28 is in communication with a return port 32 by way of passage 34. Annular channels 26 and 30 communicate with an inlet port 36 through passages 37, 38 and 40. The control valve shown in FIGURES 1 `and 2 is an open center type valve which in the neutral position allows free ow of the hydraulic fluid between the inlet port 36 and the return port 32 via the annular channels 26, 18 and 28 and via the annular channels 30, and 28.

Sealing bushings 42 and 44 are located at reduced ends 46 and 48 of the valve member 16 to provide reaction chambers 50 and 52. These reaction chambers are in effect hydraulic pressure reaction means built into the control valve in order to oppose movement of the valve member 16 away from its neutral position. In other annata Patented ,italy 26, 1965 ice words, the hydraulic pressure communicated to these chambers via passages 51 and 53 acts on the valve member tending to oppose relative movement from neutral and when such movement occurs, helps to restore the spool to its mechanical center. The spring package, which mechanically locates the spool 16 within the housing bore 14, consists of a spring 65, spring seats 61 and 63, and assorted spacers 5S, 57, and 59.

Bushing 42 is retained in the bore 14 by an end cap 153 and plate 54 which engages the outer side of the bushing. Bolts 56, only one of which is shown, secure the end cap and plate to the housing member 12. The bushing 44 includes a flange 58 which engages a shoulder 60 formed in a counterbore 62 located at the end of bore 14. A spacer ring 64 is arranged in the counterbore between the angeSS and inner end 66 of sleeve 68. A ring-like member 76 slides over the sleeve 68 for engagement with a shoulder 72 formed at the inner end 66 of the sleeve for securing the sleeve 68, spacer ring 64, and bushing 44 in assembled relationship. Bolts 74, only one of which is shown, holds the ring 78 against the end of the housing member.

The valve spool 16, which is operatively connected to a ball stud 76 for sliding movement in the bore, can be .shifted by applying a force laterally on the ball stud 94 which force must overcome the preload of spring 65. The connection to the stud is an assembly of parts comprising a bolt 78 extending through a central passage 80 of the valve member, a stop bushing 82 having an opening 84 therein which passes a small diameter of the bolt but not the enlarged end 86, an inner `sleeve 88 the inner end of which threadedly engages the stop bushing 82, members 90 and 92 providing sockets for a spherical end 94 of the stud, a spring 96, and a ball socket member 98. With nut 168 tightened down against the end 46 of the valve member, movement of the ball stud will cause the valve member and assembly to move as a unit in the housing member 12 and sleeve 68. The inner end of the sleeve 68 is slotted at 102 and 104 to receive the ends of pin 106 thereby preventing rotation of the assembly in the bore. The pin 106 passes through the stop bushing 82 and enlarged end 86 of the bolt 78 in order to prevent the latter from turning when the nut 10i) is applied thereto. The bushing 82 has a collar 108 to aid in assembly.

Note that the stop bushing 82 has a radially extending flange 168 which engages the inner end 66 of the sleeve 68 when the valve member is moved to` the right, as viewed in FIGURE 1, and the outer side of sealing bushing 44 when the valve member is moved to the left. This positive engagement between the stop bushing 82 and the sleeve 68 after a predetermined movement of the valve member permits manual steering in the event of power failure. The end of sleeve 68 is threaded at 110 so that it may be connected to the end of a cross tie rod (not shown). The sidewall of the sleeve 68 is provided with an axially extending opening 112 to permit movement of the ball stud as explained above.

ri`he invention claimed herein concerns the use of a mechanism located in the housing member for controlling the pressure differential at the cylinder ports 22 and 24. More particularly, referring to FEGURE 2, it will be seen that the mechanism 126 includes a centering plunger 122 which is slidable in a bore 124. Movement of the plunger will occur upon rotation of threaded member 126, said movement being opposed by a spring 128 which abuts a stop member 136. The bore 124, which intersects passages 38 and 46, forms orifices 132 and 134 therewith, the effective areas of which may be varied by lands 136 and 138 formed on the centering plunger 122. Thus, orifice 132 is interposed in the passage between inlet port 36 and annular inlet channel 26,

s scopeof theappended claims@ Y es Y s while orifice -134 is interposed in the passage between inlet port 36 and annular inlet channel 3:0;V If the centering plunger 122 is causedto move towards theleft by rotation of'4 threaded member 126, the effective area. oforifibe, 132,' will increase, while lthe effective area of orifice 134 will simultaneously"correspondingly decrease.. If the centering plunger 1 22 is caused to move towards ther right, the reverse vwould be true.v AsV rpre vic n1 sly stated, due to manufacturing tolerances, it is almost .im-I possible to accurately loca'ie and mechanically. center thevalve spool in the Valve housing bore so as' to insure that the proper differential pressure will exist at the cylinder ports Z2 and 24 forthe normally neutral or straight ahead 'drivingV position. ,Aceordingly, vthrough vmeans ot'y the mechanism `described, itis possible to simultaneously for simultaneously increasing the effective area of one of Asaid orificesvwliile correspondingly reducing the effective area of the other of said orices.

2. A control valve comprising a housing member having a bore therein, a spool type valve meme ber movable in opposite directions from a normally vary the effective areas of orifices 132 and 134 so as to offset variations. in the effective areas of orifices. a, b,c.

abil/OT. d which. may Y arise' because cf manutacturina tolerances,v and. thereby changewithina limitedv range.

the differential cylinder port pressureltova desired value without any increase or decrease vin lthe Vinlet pressure. -v

The severalpractical advantages whichjflow from Ymy neutral position Within said b'ore, three annular channels formed in said bore, two |annular channels formed on said valve member, said annular channels being arranged :to communicate with each other when said valve member is in said neutral position, an inlet port,'an outlet port, land two cylinder ports,. first passage means located in said housing member for communicating said inlet port with two ofthe annular 'hanneleformed in said bore, ,second V'passage means located i n saidhousingmember for communiatingsaid oulertpo'rft withlthe remaining annular channel formed in said bore, third passagemeans located insaidl housing member, for vcommunieating"one of said cylinder ports with :one'of ,the annular channels formed onvsaid lvalve member, fourth. passage means located in t said housing member .for communicating the other of invention are'beiieved 4tobe obvious from the above, J

and other advantages .may suggest'themselvesfto those" who are' familiar with the art'to which this invention macs., y J

Although'thisinvention has been described in conn'ec: tion with a .specific embodiment, it will be obvious toV those skilled in the art that various changesmay be made in the form, structure and arrangement of parts without departingfrom they spirit o f thepinvention. AccordY ingly, lv do notdesire to-be limited tothe specific embodi-v nientr disclosed herein,prirnarily for purposes vof illus-s tration, but instead ,desireY protection falling within Athe Having thus described the various features o f the in'- vention, what IA claim` as new -and desire to secure 'by- IettersPatenti's; s l f 1. A control valve comprising a housing member hav,- ing aboretherein, a ,spool type valvernember movable in oppositedirectionsfrom asnorrnally neutral position within said bore, an inletport, an outlet port and two cylinder ports, first and second Vannular inlet-channels and Aan annular outlet chann'el'lo'cated .therebetween formed in saidlbore, first passage means located in saidg housing member for communicating said inletk port with both` of said annular inlet channels, second passage means located in said.Y housing member for communicating said outlet port, with lsaid .annular outlet `channel;A first and vsecond annular cylinder :channels formed on said `valve kmember, eachofVwhich located betweenl one Aof the annular, inlet channels and the annular outlet'- channel vto permit direct fluid flow kfrom said inlet portv to said outlet portlwhentsaid valve member is in said neutral position, third passage "means vlocated in 4said housing member Vfor VcommunicatingV one of said cylinder ports with one of the annular'cylinder channels, fourth passage means located in fsaidf housing 'member for vcom-V meansfor varying the effective areas yof said first andr e second orifice means vto control the pressuredifierential at said firstand second cylinder ports, said means including a single `manually movable centering plunger said cylinder ports with 'theother'of the annular channels formed on saidfivalvejmember, first orifice `means Ainter-posed in said 'f ir'st passage means for regulating the flow of vfluids from vsaid inleteportfto oney of the two annular channels with which the `inlet port communicates, secondr orifice means interposed. in vsaid first passage means for 4regulating theflfow o f fluid from said inlet port to the other of the two annular channels with which the inlet port communicates, and plunger means located in f said first passage means fo'r'siniultaneously varying the effective areasof said first l and second orifice meansito control the pressure differential at said first and second cylinder ports. 1-

3. A control valve comprising a housing memberhaving Ia bo're therein, avalve memberl movable in opposite directions from a normally neutral position'within said bore,` a plurality of annular channels formed in said bore and@ Said valve member, Said. annular ,Channels includingtwo'annular inlet channels, an annular Qutlet` channel and'two'annu'l'ai" cylinder channels which'are arranged to permitcontinuousiluid cqmlnunication between said ,annular inlet channels andV said' annular outlet channel ber is in saidneutralposition, an inlet port,an outlet port and two cylinder parts,- passage means located in said housing member for communicating said linlet, 'outlet and cylinder ports Vsaid inlet`,ontlet .and cylinder channelsvrespectively, first orifice 'means interposed in said passage means forregulatingthe. flow 'of fluid from said inlet port to one otsaid' annularr inlet channels, second orifce A'means interposed in said 'passage means for regulatingthe flowofuid from said inletv por.; to the other of'said annularinlet channels, and plunger means lctsdlinsid Passes@v means for ,Simultaneously .varying t the eective areas Vof saidfirstfand second orifice. means tofcontrol the pressure v difierentia-l at said first and second Cylinder parts-v f f References Cited; thefExaminer A 'Y UNTTED STATES PATENTS Y 

1. A CONTROL VALVE COMPRISING A HOUSING MEMBER HAVING A BORE THEREIN, A SPOOL TYPE VALVE MEMBER MOVABLE IN OPPOSITE DIRECTIONS FROM A NORMALLY NEUTRAL POSITION WITHIN SAID BORE, AN INLET PORT, AN OUTLET PORT AND TWO CYLINDER PORTS, FIRST AND SECOND ANNULAR INLET CHANNELS AND AN ANNULAR OUTLET CHANNEL LOCATED THEREBETWEEN FORMED IN SAID BORE, FIRST PASSAGE MEANS LOCATED IN SAID HOUSING MEMBER FOR COMMUNICATING SAID INLET PORT WITH BOTH OF SAID ANNULAR INLET CHANNELS, SECOND PASSAGE MEANS LOCATED IN SAID HOUSING MEMBER FOR COMMUNICATING SAID OUTLET PORT WITH SAID ANNULAR OUTLET CHANNEL, FIRST AND SECOND ANNULAR CYLINDER CHANNELS FORMED ON SAID VALVE MEMBER, EACH OF WHICH IS LOCATED BETWEEN ONE OF THE ANNULAR INLET CHANNELS AND THE ANNULAR OUTLET CHANNEL TO PERMIT DIRECT FLUID FLOW FROM SAID INLET PORT TO SAID OUTLET PORT WHEN SAID VALVE MEMBER IS IN SID NEUTRAL POSITION, THIRD PASSAGE MEANS LOCATED IN SAID HOUSING MEMBER FOR COMMUNICATING ONE OF SAID CYLINDER PORTS WITH ONE OF THE ANNULAR CYLINDER CHANNELS, FOURTH PASSAGE MEANS LOCATED IN SAID HOUSING MEMBER FOR COMMUNICATING THE OTHER OF SAID CYLINDER PORTS WITH THE OTHER OF SAID ANNULAR CYLINDER CHANNELS, FIRST ORIFICE MEANS INTERPOSED IN SAID FIRST PASSAGE MEANS FOR REGULATING THE FLOW OF FLUID FROM SAID INLET PORT TO ONE OF SAID ANNULAR INLET CHANNELS, SECOND ORIFICE MEANS INTERPOSED IN SAID FIRST PASSAGE MEANS FOR REGULATING THE FLOW OF FLUID FROM SAID INLET PORT TO THE OTHER OF SAID ANNULAR INLET CHANNELS, AND MEANS LOCATED IN SAID FIRST PASSAGE MEANS FOR VARYING THE EFFECTIVE AREAS OF SAID FIRST PASSAGE SECOND ORIFICE MEANS TO CONTROL THE PRESSURE DIFFERENTIAL AT SAID FIRST AND SECOND CYLINDER PORTS, SAID MEANS INCLUDING A SINGLE MANUALLY MOVABLE CENTERING PLUNGER FOR SIMULTANEOUSLY INCREASING THE EFFECTIVE AREA OF ONE OF SAID ORIFICES WHILE CORRESPONDINGLY REDUCING THE EFFECTIVE AREA OF THE OTHER OF SAID ORIFICES. 